1. Field of the Invention
The invention relates to an X-ray tube, comprising a cathode for generating an electron beam and an anode, having a comparatively thin anode target layer, for generating X-rays in response to the impingement of the electron beam, and also comprising an X-ray exit window.
2. Discussion of the Related Art
An X-ray tube of this kind is known as a target transmission tube from U.S. Pat. No. 4,969,173. An X-ray tube described therein comprises a radiation exit window which is made of, for example beryllium and an inner side of which is provided with a thin layer of metal which acts as the anode target layer. In the anode target layer notably the X-rays are generated, which X-rays emanate directly via the exit window in this case.
A thin anode target layer of this kind may also be provided on an anode support of a suitably thermally conductive material mounted in an X-ray tube. In the case of such thin anode target layers, the degree of dissipation of the heat generated by the incident electron beam has a strong effect on the service life of the tube. This problem is significant in target transmission tubes because of the comparatively poor thermal conductivity of the thin anode target layer itself as well as of the comparatively thin beryllium exit window. In the case of anode target layers provided on a metal anode support the problem of locally excessive temperatures may arise because the transition between the anode target layer and the anode support constitutes a heat barrier.